Fluidic potentiometer

ABSTRACT

A fluidic potentiometer having a slidable member adapted to slide with respect to a passage containing fluid under pressure and sense the pressure of fluid at any point along said passage, along with means for providing an output signal corresponding to the pressure sensed.

A United States "Patent llll. 3,554,229

[72] lnventor Vincent E. Coyle [56] References Cited Wayne, J- UNITED STATES PATENTS [21] 785.373 2,833,311 5/1958 Baldelli 138/43 [221 PM xx-19,1968 2 840 096 6/1958 DUBOiS l38/43X [451 3'148703 9/1964 Kacmin i i i 137/608 bcenenl Precision Inc. [731 8 3,150,686 9/1964 Kachlme 2 137/608 I 3,373,772 3/1968 l-lilgert 138/43 3,429,323 2/1969 Mott 137/815 3,461,833 8/1969 Boyadjiefi l37/81.5X Primary Examiner-Samuel Scott [54] Attorneys-S. A. Giarratana, G. B. Oujevolk and S. M. Bender l37/8l.5 ABSTRACT: A fluidic potentiometer having a slidable [51] Int. Cl Fl6d 1/00, member adapted to slide with respect to a passage containing 1 Fl5c 3/00 fluid under pressure and sense the pressure of fluid at any [50] Field of Search 137/815, point along said passage, along with means for providing an 608 output signal corresponding to the pressure sensed.

PATENTEBJAN12I971 3554.229

INVENTOR VINICENT E. COYLE A T TORNEY FLUIDIC POTENTIOMETER BACKGROUND OF THE INVENTION This invention relates to a fluidic potentiometer and, more particularly, to such a potentiometer which provides a detec'table fluid pressure output which varies in response to variations in an input signal.

Several devices have been proposed for providing a fluidpressure or flow which varies in response to variations in an input signal. For example, it has been proposed to provide a .fluid orifice which is effectively varied in size by inserting a SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a fluidic potentiometer which operates linearly, and which is of a relatively high sensitivity.

It is a further object of the present invention to provide a fluidic potentiometer which is easily manufactured and is of a simple construction. 7

Briefly summarized, the fluidic potentiometer of the present invention comprises a passage means for the flow of fluid under pressure, a slidable member adapted to slide with respect to said passage means and sense the pressure of fluid at any point along said passage means, which pressure is proportional to the position of said slidable member with respect to the passage means, and means for providing an output signal corresponding to the pressure sensed.

BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawings for a better understanding of the nature and objects'of the fluidic potentiometer of the present invention, which drawings illustrate the best mode presently contemplated for carrying out the objects of the invention and its principles, and are not to be construed as restrictions or limitations on its scope. In the drawings: 7

FIG. 1 is a perspective view of the fluidic potentiometer of the present invention;

FIG. 2 is a vertical cross section taken along line 2-2 of 'FIG. 1;

FIG. 3 is a vertical cross section takenialong line 3-3 of FIG. 1; and I FIG. 4 is a top plan view of a component of the fluidic potentiometer of the present invention. I

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to FIGS. 1-4 which depict the fluidic potentiometer of the present invention, the reference numeral refers to an elongated fixed body member which has a slide member 12 extending between it and a fixed collector plate 14 with the adjacent surfaces of the respective components in engagement, as shown. I

A pair of grooves 16 and 18 are provided in the upper surface of the body member 10, it being understood that these grooves have dimensions that permit laminar flow of a fluid, such as air to be established therethrough, as will be discussed in detail later.

A pair of ports 20 and 22 are provided in the slide member 12 and are adapted to register with the grooves 16 and 18, respectively, when the slide memberis placed over the body member. Therefore, the ports of the slide member tap off a pressure from each groove that is proportional to the position of the slide member with respect to the fixed body member.

vA pair of grooves 24 and 26 are provided in the collector plate 14 which. register with the ports 20 and 22 in the slide member 12 to pick off the pressure iri'ea'ch of the ports 20-and' 22 and transfer it to the outside of the assembly through a pair of output ports 24a and 26a disposed at the ends of the grooves 24 and 26, respectively, and terminating at opposite ends of the plate 14, as shown in FIGS. 2 and 3. It is understood that these output pressures may be combined to'form a differential pressure and can be used to drive an external component, such as fluidic amplifier, or the like.

The potentiometer of the present invention may be mounted in a position shown in FIG. 2, with a spring 30 fixed to a fixed surface 32 engaging the upper surface of the collector plate 14 and urging the assembly toward a second fixed surface 34, and thus spring loading the assembly.

In operation, the slide member 12 is'physically attached to any type ,of movable member, such as the output shaft of a piston actuator or the like, and a fluid is supplied under pressure from an external source (not shown) at opposite ends of the grooves 16 and 18 as shown in FIG. 4 by the arrows A. Laminar flow thus occurs through the grooves and the pressure at any point in a groove, as detected by the ports 20 and 22 and transferred to the output ports 24a and 26a is directly proportional to the distance from that point to the return end of the groove, divided by the total groove length. Movement of the armature, and therefore the slide member, in response to variations of the inputsignal will cause the slide member to slide with respect to the body member 10 and the collector plate 14, to vary the fluid pressure available at the output ports 24a and 26a.

It has been ascertained .that witha supply pressure of about 1 p.s.i.a., a groove 0.050 inches by 0.050 inches formedin the body member 10 will givea laminar flow of air, and can be used to supply afluidic amplifier with a flow rate of approximately 0.025 s.c.f.m., with linearity of 1 percent or better.

It is thus seen that the fluidic potentiometer of the present invention provides a linear operation utilizing a laminar flow principle that is extremely sensitive, and is easily manufactured and assembled. Also, the components may be made of a strong material, such as metal, and the lapped surfaces between the adjacent components of the assembly adjacent the grooves, along with the spring loading, minimize leakage.

Several variations in the potentiometer of the presentinvention may be made without departing from the scope of the invention. For example, the grooves may be shaped in any manner in accordance with the design requirements of the particular system. For example, they may be shaped to provide nonlinear outputs to compensate for any nonlinearities in the input.

Also, only one groove may be formed in the body member 10, in which case one port will be formedin the slide member 12, and one groove formed in the collector plate 14, in the event a differential pressure .is not necessary.

Of course, the shape of the body member and its associated slide member and collector plate may be varied as-desired. For example, the-body member may be curved into a substantial circle with the slide member and the collector member shaped accordingly.

Of course, other variations of the specific constructionand arrangements of the fluidic vpotentiometendisclosed above can be made by those skilled in the art without-departing'from the invention asdefined in the appended claims.

I claim:

l. A fluidic potentiometer for sensing mechanical displacement of a body comprising a first member having a first passage means and a second passage means, said first and second passage means being arranged for the flow of fluid under pressure through each in opposite directions, and a second slidable member-adapted to slide with respect to said first member and said first and second passage means and sense the differential pressure of fluid at any point along'said first and second passageiineans between respectiveadjacent first and second portions thereof, which differential pressure is proportional to the position of said second slidable member with respect to the first member and the first and second passage means, and a third member fixedly positioned relative to said first member and adapted to provide an output-signal corresponding to the differential pressure sensed by the said second slidable member.

2. The potentiometer of claim 1 wherein said second slidable member has a first port and a second port formed therein which are adapted to register respectively with said first and second passage means to tap off the differential pressure between said first and second portions of said first and second passage means at all positions of said second slidable member with respect to said first member and said first and second passage means, and wherein said first and second and third members are elongate members, and wherein said first and second passage means are elongate passage means which are disposed substantially parallel to each other.

3. The potentiometer of claim 2 wherein said third member which is operative to provide an output signal cooperates with said second slidable member to provide an output signal corresponding to the differential pressure tapped off by said first and second ports of said second slidable member, and wherein said first and second and third members are substantially flat plates, and wherein said second slidable plate is disposed between said first and third plates, and wherein said first and third plates have support means.

4. The potentiometer of claim 3 wherein said third plate is a fixed plate extending over said second slidable member, said third plate having a substantially flat surface having a first groove and a second groove formed therein which respectively register with said first and second ports and having first and second output ports respectively registering with said first and second grooves.

5. The potentiometer of claim 4 wherein said first and second passage means respectively comprise first and second elongate notches formed in a substantially fiat surface of said first fiat member.

6. The potentiometer of claim 5 wherein said first and second notches are dimensioned to permit a laminar flow of fluid therethrough, so that said differential pressure is directly proportional to the position of said second slidable plate member with respect to said third plate member and said first plate member and said first and second passage means, and wherein said support means has a first surface engaging said first plate and has a second surface disposed adjacent to said third plate, and wherein said support means includes spring means disposed between said second support surface and said third plate for urging said first and third plates in bearing against said second plate. 

1. A fluidic potentiomEter for sensing mechanical displacement of a body comprising a first member having a first passage means and a second passage means, said first and second passage means being arranged for the flow of fluid under pressure through each in opposite directions, and a second slidable member adapted to slide with respect to said first member and said first and second passage means and sense the differential pressure of fluid at any point along said first and second passage means between respective adjacent first and second portions thereof, which differential pressure is proportional to the position of said second slidable member with respect to the first member and the first and second passage means, and a third member fixedly positioned relative to said first member and adapted to provide an output signal corresponding to the differential pressure sensed by the said second slidable member.
 2. The potentiometer of claim 1 wherein said second slidable member has a first port and a second port formed therein which are adapted to register respectively with said first and second passage means to tap off the differential pressure between said first and second portions of said first and second passage means at all positions of said second slidable member with respect to said first member and said first and second passage means, and wherein said first and second and third members are elongate members, and wherein said first and second passage means are elongate passage means which are disposed substantially parallel to each other.
 3. The potentiometer of claim 2 wherein said third member which is operative to provide an output signal cooperates with said second slidable member to provide an output signal corresponding to the differential pressure tapped off by said first and second ports of said second slidable member, and wherein said first and second and third members are substantially flat plates, and wherein said second slidable plate is disposed between said first and third plates, and wherein said first and third plates have support means.
 4. The potentiometer of claim 3 wherein said third plate is a fixed plate extending over said second slidable member, said third plate having a substantially flat surface having a first groove and a second groove formed therein which respectively register with said first and second ports and having first and second output ports respectively registering with said first and second grooves.
 5. The potentiometer of claim 4 wherein said first and second passage means respectively comprise first and second elongate notches formed in a substantially flat surface of said first flat member.
 6. The potentiometer of claim 5 wherein said first and second notches are dimensioned to permit a laminar flow of fluid therethrough, so that said differential pressure is directly proportional to the position of said second slidable plate member with respect to said third plate member and said first plate member and said first and second passage means, and wherein said support means has a first surface engaging said first plate and has a second surface disposed adjacent to said third plate, and wherein said support means includes spring means disposed between said second support surface and said third plate for urging said first and third plates in bearing against said second plate. 